The MVP of the playoffs has obviously been Dirk Nowitzki ... unless it's been LeBron James. The two stars have led their respective teams to the NBA Finals with impressive postseason performances. That begs a question as the NBA Finals get set to tip off: Which player is more important to his team?

Overall Performance

Nowitzki's argument is built around the fact that he has been the league's best scorer in the playoffs. Most go-to players see their efficiency decline as defenses load up against them, but Nowitzki has actually improved his true shooting percentage from .612 to .640 while playing a larger role in the Dallas Mavericks' offense. No one else can come close to touching Nowitzki's combination of ability to create shots and knock them down during the postseason. The league's other leaders in usage rate, James included, have been far less efficient than Nowitzki.

While James can't touch Nowitzki's scoring, he's built a case as the best player in the playoffs on his versatility. James is averaging 26.0 points, 8.9 rebounds and 5.5 assists and ranks among the league's top five in such diverse totals as free throws, defensive rebounds, blocks, steals and points. During the series with the Chicago Bulls, James' defense might have been as important as his offense. LBJ shut down regular-season MVP Derrick Rose in key moments, holding him to 6.3 percent shooting when the two players matched up, per ESPN Stats and Information.

Depending on what player metric is considered, a case can be made for either James or Nowitzki. Nowitzki ranks second in playoff PER to long-departed Chris Paul, his 27.3 mark putting him just ahead of James (26.9). However, James takes the upper hand in Estimated Wins Added, a measure of total value, because he's played more minutes per game. Basketball Prospectus' wins above replacement measure, which places more weight on defensive statistics, has James ahead on a per-minute basis with a wide gap in terms of total value: James rates as 4.6 wins better than a replacement-level player, while Nowitzki rates as 3.2 wins better. James also edges out Nowitzki in win shares per 48 minutes, .252 to .243.

Clutch Performance

Both the Mavericks and the Heat have used a series of close victories to get to this point, and they've relied on their stars late in games. Clutch statistics from NBA.com's StatsCube--which defines clutch as the last five minutes of games with a margin of five points or fewer--reveal how effective James and Nowitzki have been in these situations.

The most amazing number for Nowitzki might be this: In 32 clutch playoff minutes, he's yet to turn the ball over. In addition, Nowitzki has been outstanding at drawing fouls late in games, attempting 25 free throws in 32 minutes in clutch situations and making 24 of them. (Part of this is that Nowitzki's uber-accurate free throw shooting makes him valuable late in close games when opponents are forced to foul.) As a result, though Nowitzki shoots no better late in games than overall, his true shooting percentage has improved from .640 to .769 in these situations.

The key to James' late-game performance in the playoffs has been his complete control of the Miami offense. James' usage rate in clutch situations has been 47.1 percent, meaning he's responsible for basically every other Heat trip down the floor with games on the line. In both the Boston and Chicago series, James has relied on uncanny long-range shooting to bring Miami back or put games away. Nearly a third of his shot attempts (10 of 31) have been 3s, and James has knocked down five of them.

Indispensability

The most unlikely statistic from the playoffs might be this: The Heat has actually actually been better with James on the bench during its run to the NBA Finals. There are several reasons for that, including both the poor performance of Miami's starting lineup before Joel Anthony replaced Zydrunas Ilgauskas and the limited time James has spent on the bench--70 total minutes in 15 games. However, it does reflect one important difference between the roles James and Nowitzki play for their teams. On the rare occasions James rests, the Heat can turn to two other All-Stars. Dallas depends much more heavily on Nowitzki.

During the regular season, the Mavericks were 16.2 points better per 100 possessions with Nowitzki on the court. Per BasketballValue.com, that was the league's third best net plus-minus. As well as Dallas' reserves have played in the playoffs, the same trend has continued. The Mavericks have been outscored by 23 points with Nowitzki on the bench.

StatsCube's breakdowns indicate that Jason Terry steps into the role of go-to scorer when Nowitzki rests, increasing his shot attempts per 36 minutes from 12.9 to 18.0 in the playoffs. The larger role comes with a price in terms of accuracy. Relatively fewer of Terry's shot attempts are 3-pointers, and he has made them at just a 24 percent clip compared to 54 percent with Nowitzki drawing the defense and setting him up. Jason Kidd also feeds on shots created by Nowitzki. Kidd has made 24 percent of threes with Nowitzki on the bench but 39 percent with him on the floor.

By contrast, Dwyane Wade can pick up the extra shot attempts when James goes to the bench. Wade has averaged 29.8 points per 36 minutes during the playoffs without James, as compared to 20.8 alongside him. His shooting percentages take a slight hit, but nowhere near as dramatic as the Mavericks' guards. During the regular season, Wade was just as efficient with James resting.

Because of Nowitzki's age, Rick Carlisle likes to give him a break in both halves. The most minutes Nowitzki has played in regulation in the playoffs has been 42--less than James' average of 44 minutes a night. How Dallas is able to handle the time Nowitzki spends on the bench may go a long way toward determining the outcome of the series.

Kevin Pelton is an author of Basketball Prospectus.
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